﻿Variation in the Norway Lobster. 



139 



3. On Variation in the Number and Arrangement 

 OF THE Male Genital Apertures. 



For this purpose 4429 Norway lobsters were examined. 

 It was indeed this part of the examination that led to a 

 consideration of the two points just discussed. Dr Marshall, 

 in the paper already referred to, says " That Norway lobsters 

 with additional genital apertures have been common in 

 Scottish waters for a considerable number of years, appears 

 from information supplied me by Professor Ewart, Dr Beard, 

 Dr Masterman, and others," and "Dr Beard, who has had 

 occasion to examine a very large number, speaks to me of 

 regular epidemics of this kind of abnormality in some years 



Table IV. 



Numbers of Abnormal Males. 



Different Lots. 



Total Males. 



Normal Males. 



Abnormal 

 Males. 



Percentage of 

 Abnormality. 



"Zool. Lab. ' 



1249 



1167 



82 



6-6 



Lot B. 



771 



739 



32 



4-2 



Lot C. 



361 



351 



10 



2-8 



Lot D. 



90 



89 



1 



1-1 



Lot E. 



232 



208 



24 



10-3 



Lot F. 



173 



164 



9 



5-2 



Lot G. 



620 



565 



55 



8-9 



Lot H. 



933 



859 



74 



7-9 



Total, 



4429 



4142 



287 



6-5 



in the past" (page 8). In an examination in 1901 of 1000 

 male specimens in the Zoological Department of Edinburgh 

 University, Dr Marshall found that 12 '2 per cent, were 

 abnormal in this respect. It was chiefly to test whether 

 this high percentage is still maintained that the present 

 investigation was begun, and as the 1249 " Zool. Lab." 

 specimens here considered were procured under exactly 

 similar conditions, the comparison is at least interesting. 

 The results are summarised in Table IV., where it is shown 



